The present invention relates of a device for measuring the momentum of a dense particle, such as a stone, gravel particle, ball bearing, or the like, being carried by a moving fluid such as air, water, fuel, lubricant, etc., and particularly to a device for measuring momentum of gravel particles moving in a stream, surf or down a steep hillside.
The prior art includes particle sensors for sensing the number of particles being carried by a stream. This type of sensor is a hollow cylinder or pipe designed to have one end embedded in a stream bed with its other end extending into the moving water. Impacts or pings produced by gravel particles impinging on the upper end of the sensor are counted. Mass and volume transport of gravel in the stream can be calculated from the ping count when average particle size and weight are known. However average particle size and weight are often not known or often change when stream conditions change.
A sensor for determining the energy (momentum) of sand or fracture particles in oil and gas production flow streams is known in the prior art. This sensor determines the area within the acoustic vibration envelope produced by impingement of a particle on cylindrical probe extending into the pipe carrying the flow stream to determine the particle energy.
An object of the invention is to construct an improved particle momentum sensor for measuring the momentum of dense particles, such as a stone, gravel particle, ball bearing, or the like, being carried by a moving fluid such as air, water, fuel, lubricant.
Another object of the invention is to enable detection of the momentum of closely spaced particles in a moving fluid.
These and other objects are achieved in a particle momentum sensor having a massive support with a flat surface on which is mounted a piezoelectric member supporting a flat low mass plate resistant to deformation by impinging particles and having a rigidity suppressing multiple mode vibration of the plate. The piezoelectric member generates a damped oscillating electrical signal when a particle impinges upon the plate. A circuit integrates a portion of the damped oscillating electrical signal to determine momentum of the particle.
Additional features of the invention include the integration of the first half cycle of the damped oscillating electrical signal to determine particle momentum; a system Q of about 2 to enable detection of closed spaced particles; a fundamental oscillating frequency of the plate and its mounting being sufficiently high such as 10 kHz to 20 kHz for enabling detection of closely timed impingements of particles; the use of two flat plates or joined plate portions disposed at an angle such as 90xc2x0 relative to each other; and the mounting of the piezoelectric member with the flat plate in a recess in one side of a metal bar having a rectangular cross section.
Other advantages and features of the present invention will be apparent from the following detailed description and the accompanying drawings.